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<br /> <br /> <br /> <br />Frank DeMarco <br />Harry Kim <br />Director <br />Mayor <br /> <br /> <br /> <br /> <br /> <br />Allan Simeon <br />Wil Okabe <br /> <br /> <br />Deputy Director <br /> Managing Director <br /> <br /> <br /> <br />County of Hawai‘i <br /> <br />DEPARTMENT OF PUBLIC WORKS <br />Aupuni Center <br />101 Pauahi Street, Suite 7 · Hilo, Hawai‘i 96720-4224 <br />(808) 961-8321 · Fax (808) 961-8630 <br />www.co.hawaii.hi.us <br /> <br /> <br /> <br />Date: June 8, 2017 <br /> <br />Code/ Edition: 2008 National Electric Code (NEC) <br /> <br />Subject: PV Electrical Review <br /> <br />The following is a list of design requirements that are most easily overlooked in the design <br />phase. <br /> <br />A) Ambient Conditions <br />1) Module Open Circuit Voltage – NEC 690.7 <br />i) The open circuit voltage listed on the manufacturer’s specification sheet is only valid <br />for the standard test conditions. When the temperature decreases, the module <br />voltage increases, this increase poses the greatest issue with maximum string <br />lengths, and maximum voltage input on the inverter. As the temperature increases, <br />the module voltage decreases, and may not create a high enough voltage to turn on <br />the inverter. <br />2) Rooftop conductor de-rate – NEC Table 310.15(B)(2)(c) <br />i) Depending on the conduit height above the roof, the conductors will be subject to a <br />de-rate. <br />3) Conduit Expansion – NEC Table 352.44 <br />i) PVC conduit subject to a change in temperature will expand and contract as the <br />temperature changes. <br />B) Warning Labels <br />1) Labels and Marking - NEC 690.5(C) <br />WARNING <br />ELECTRIC SHOCK HAZARD <br />IF A GROUND FAULT IS INDICATED <br />NORMALLY GROUNDED CONDUCTORS <br />MAY BE UNGROUNDED AND ENERGIZED <br />2) Bipolar Source and Output Circuits – NEC 690.7(E) <br />County of Hawai‘i is an Equal Opportunity Provider and Employer. <br /> <br />